Acacia College, Mernda, Victoria

Project 3 of 8

Project Overview

Acacia College is located at 370 Bridge Inn Road Mernda a 45 km drive north of Melbourne. The college is a new co-educational facility which caters for students from Prep to Year 12.  The College opened on 1 February 2010 with a 121 student population with classes provided for Prep to Year 7 level.  During 2010, the Foundation Year, enrolments have increased dramatically and by 2015 the college expects to have 1,300 students across all levels Prep to Year 12; with a further 250 children in childcare and kindergarten facilities.

There are a further five stages to the college as well additional stages for the project that include a gymnasium, childcare centre, kindergarten, swimming centre and basketball stadium which we expect to complete over the next 4 years.  Direct Energy Geothermal Heat Pumps are expected to be included in these future stages.  Direct Energy is supplying the building’s heating and cooling requirements and the proposed use of geothermal swimming pool heating.



System Selection

Stage 1 and 2 of Acacia College were designed by McCabe Architects employ 504 kW of heating & cooling capacity dispersed over the following buildings:

  • Administration building (668m²)
  • •Junior School class room building (1870m²)
  • Middle School double-level class room building (2625m²)
  • Worship Centre (1048m²)

Direct Energy was engaged in August 2009 to provide refrigerated ducted heating and cooling to the above described buildings.  The first 2 stages consist of 24 x 21kW geothermal heat pumps, including a total of 144 x 30m copper ground loops which have been installed and connected to the geothermal heat pumps.


Mernda has a typical four-season climate, with hot dry summers and cold wet winters. The temperature ranges from 3 °C to 42 °C, while mean minimum daily temperature ranges from 15°C  to 6 °C.

Heating and Cooling

The heating & cooling is designed to maintain a comfortable temperature within the range 20 °C to 24 °C and is capable of providing additional heating or cooling if required. Public areas are required to be conditioned 8am – 5pm five days a week. There are also various after hours activities during which aspects of the building are used considerably more frequently.

Due to their considerable ongoing operational savings Geothermal Heat Pumps were considered as the primary option from the outset of the design of the buildings.

24 x 21 kW GHPs were selected for their energy and cost savings, ease of operation and reliable comfort.

Energy Savings

Energy costs and savings are an important part of any air conditioning decision, and they are expected to become more important as energy costs rise.

GHPs cut energy use and operating costs. The total annual energy consumption, covering both heating and cooling cycles, for the GHP system is expected to be under  ½  of that consumed by the alternative option.

The GHP system is nearly twice as efficient as the roof-top package and over five times more efficient than LPG heaters.

Cost Savings

The annual cost of operating the GHP air conditioner is commonly less than 50% of the cost of the alternative. The capital cost of the GHP system was higher than that for the alternative by the cost of drilling & ground loops. However, when the capital cost and annual operating costs are considered, the time to pay back the additional capital cost is expected to be within 3-4 years.

Energy Price increases will shorten the pay-back period.

Geothermal Heat Pumps are noted for their reliability and long life.

Warranties of 20 years on the ground loops and 5 years on the plant have been provided. The ground loops are anticipated to have a life of more than 50 years and the plant a life of up to 25 years or more.

Environmental and Safety Performance

Geothermal Heat Pumps are the best environmental option, considering:

  • •Greenhouse gas emissions – 30% less than the alternative
  • Quietness <50dB
  • •Aesthetics and security – inside or outside options available as GHPs do not require ventilation

Ease and safety of operation – automatic operation via wall thermostats.



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